Thursday, November 18, 2010

While out on my run last night, I had trouble avoiding tripping over myself as I stared, slack-jawed at the incredible sunset. One of the amazing things about living here on the Front Range of the Rockies is the propensity for wave cloud sunsets, especially in winter months.

For the past couple of days, we've been in zonal upper level flow which means the jet is basically plowing across the western half of the country in a west to east fashion with out much if any amplitude. These strong upper level winds do carry a little Pacific moiture with them and are forced up over the Rockies, making a wave. In the of the mountains when the air no longer is supported by terrain, it falls, mixing down in the form of strong winds. Temperatures today were at least 20 degrees higher than those of yesterday as sinking air warmed, giving us a bit of a Chinook event. Temperatures approached 70ºF in some areas in the metro area while yesterday, they struggled to get above 40ºF.

As far as the upper levels are concerned, there is a bit of a rebound or rise in the air after sinking off of the mountains. This often materializes in the form of a standing wave cloud as the air rises and cools, condensing the moisture.

After being caught without my camera last night, I realized that we would see some wave cloud action again tonight, so planned around it. As the sun began to sink in the west and peeked out below the wave, the entire area was bathed in a golden light. I headed out with my cameras and tripods and set up shop in the empty lot east of my apartment complex. So, enough of the talking... let's see some pictures!

I also did a 42 minute time lapse video which I will attempt to convert to a usable format overnight and perhaps share tomorrow.

Speaking of tomorrow, the pattern won't change too much, though a trough is digging along the west coast. We'll see what is in store!

Wednesday, November 17, 2010

The 4.0km WRF NMM Precip model showed convection moving over the metro area today and to be quite honest, it nailed it. I love that little model!

After taking Der Schploder to the shop for a tuneup today, I walked back to my apartment in a t-shirt and jeans. With temperatures in the mid 50s, it was comfortable out, if not warm. I was surprised to see the resident prairie dog population awake and out of their burrow. They are all quite fat! ...which I suppose is normal for this time of year.

As I walked, I noticed that the mountains were being hugged by snow showers, but at their edge, everything cleared up. In fact, the skies were clear from the southern horizon to the northern, aside from one tiny cumulus cloud which cast a brief shadow on me as I dodged the alarmed chirps of the prairie dogs.

When I arrived home, I took a closer look at things. According to SPC's Mesoanalysis Page, there was at least 100J/kg MUCAPE to the northwest. After seeing the WRF model, I decided to keep a close eye on things.

Associated with the upper level system bringing some crazy snow and wind to part of Idaho and Montana, lee-side cyclogenesis appeared to be happening across the eastern plains. Winds through the metro area were mostly of a westerly component which actually helped with warming today. DIA, for example, reached 60ºF (only 55ºF at my apartment in Centennial).

An hour or two later, I noticed a nice line of returns on the radar pulsing south toward the metro area. Though the view from my apartment is obstructed by the buildings across the street, I could see that the northern sky was now clouded while the south was still completely blue.

Taking another look at the radar, I could see that the returns were quickly approaching the radar site... and strengthening. I resolved to get my camera gear and head out the door. On my way out, I received a picture message from Ben Toms showing a nice shelf on the front side of this convective squall.

I realized I would have to go without my tripod as both of them were in the car (which was in the shop), so I wandered out of my apartment complex to get a better view. I really wasn't prepared to see what the storm had in store for me. When I finally got a view, the light was just perfect to make it look like a giant wave was crashing through the area. It was incomprehensible!

The turbulence along the front edge of this storm was amazing. I felt like I had jumped into a hot tub time machine and ended up in the spring. The lift on the front of this storm was so vigorous that it took me to a different season. Eventually and unfortunately, the brilliant light on the front side was blocked by "anvil" if you will, from the western edge of the storm heading through the mountains. I held my position on higher ground and watched as the storm kicked up dust (mainly to my east) and the shelf passed.

Here was the radar at about that time:

Surprisingly up until this point, I had evaded any the wrath of this storm. This silence was short-lived, however as soon I could hear the trees to my north basically bend over, the remaining leaves rattling like maracas. It didn't take long for this wind to hit me. It was like jumping into a cold lake. I was still standing there in my jeans and a t-shirt and the temperature immediately dropped 15ºF and was accompanied by 30kt winds. (I know this because I pulled my Kestrel out and took an ob!)

The wind cut me like a knife, so I eventually made my way south to an open lot just east of my apartment complex. There, the wind picked up dust readily and lofted it. Unfortunately, due to low-contrast, I couldn't really get a great photo of this. Let's just say that the prairie dogs were no longer topside at this point.

I took a few photos from here. The first is to the west where you can see the edge of the storm along the mountains. The second is to the southeast where you can see the leading edge of the storm.

Eventually, rain with embedded bits of ice accompanied the biting wind, driving me back home. I usually like to front my climate tolerance as being extreme, citing my Montana nativity, but I'll be honest: I was freezing!

Back inside my apartment, it took a few minutes for my arms and hands to start working properly again. When I recovered, I looked outside to see a frenzy of dendrites flitting into the windows, the wind howling through my building. The flakes were quite large, perhaps two inches in diameter at the largest and the wind was blowing them around in such a manner that it evoked the feeling of staring into a snow globe... while it was being shaken.

This was short-lived, however, and after ten minutes the pavement was wet and grassy surfaces were white, but the precipitation had ceased.

What a wild storm it was while it lasted! Several of the local ASOS stations picked up winds at or near 45kt. As you can see in Johnathan Skinner's video HERE, there was quite the dust storm on the east end of the city. It's really a fantastic time-lapse.

A couple more waves of light snow and wind moved through the area before the end of the evening and while none of them left any significant accumulation, it was an interesting weather day for sure!

Saturday, November 13, 2010

Synoptics:A 548dam 500mb cut off upper level low was rotating into the Four Corners region with a 75kt 300mb jet pushing into the Panhandles region. This left SE Colorado and SW Kansas under the left exit. At the surface, models were showing complex cyclogenesis along the lee of the Rockies and deep moist upslope across the High Plains. The hodographs were beautiful along with some decent CAPE.

The night previous, we (Scott Hammel and I) were still not sure if we would be chasing in Eastern Colorado or the Texas Panhandle (the dryline play). After going out for a chase the night before and having been thinking a lot about the forecast, I was in favor of staying close to home. So, I went to bed that night not having to get up before dawn and make the trek to Amarillo.

I met up with Scott that morning and we discussed the day's possibilities and targets. Based on what I was seeing from morning models, I thought it possible to actually have two targets. The first was early convection along the warm front in Colorado and then after storms crossed the boundary and "piled up", a secondary target in Kansas as instability increased and upper level support moved in later in the afternoon. And with that in mind, we were off.

Just outside Denver, thunderstorms were already rolling northward. We passed through one near Strasburg and I was already surprised at how strong it was. Further development along our path to the south near Limon showed evidence of a lot of low level wind shear. While I wouldn't say that we saw any funnels, it was apparent that there was a serious turning in the atmosphere, especially at cloud base.

The sun was out in earnest as we headed southeast out of Limon. We were briefly delayed by road construction near Wild Horse, but made it to our initial target of Eads (Home of the Eagles) a bit after 11AM. There, we met up with Team Carlson (Michael and Eric as well as Kendell "Inspector" LaRoche) and Tim Stoecklein and just hung out on the west side of town for a little while, talking about the forecast. Michael had been on record for days about wanting to chase the setup in Colorado and it was good to see him out on the hunt!

As we were sitting there, SPC issued a mesoscale discussion (#335) which got us pretty excited. It was for areas along the stationary boundary to our south and to the north, including actually, most of the eastern plains of Colorado. It surprised me how far north they were looking (at the time) but our attentions were soon drawn to a little blip on the radar which was showing up in southern Bent County. It was south of the boundary where the dewpoints had begun to mix down into the upper 30s, but was headed toward the boundary. That's where we wanted to be, so we all set out west on Colorado 96. I knew of a nice paved shortcut that connected 96 and US50, so we set off south on that road (Kiowa CR 19) at Haswell. With a lot of clearing to our south, the storm was already visible.

Soon the tones were going off on the radio which indicated a watch (Tornado Watch #74) had been issued. We stopped on the Kiowa/Bent county line and took a few pictures of the storm, which was already looking supercellular. The storm's visible presentation already had me very excited.

As we continued on south in Bent County, we began to encounter precipitation. It was light rain at first, but as we approached US 50, we were in hail, the size of which was increasing.

Base Reflectivity (KPUX) and our position in pink at 1903Z.

The precipitation wasn't thick enough to obscure our vision, so we saw the wall cloud start to form while we were still a few miles north of US 50. Reaching the highway, we had a pretty good view, so we pulled off on the shoulder less than a half mile from the intersection of our paved route from the north. I sat there wide-eyed, as the wall cloud began to tighten and a funnel began to form. I decided to report the situation to Pueblo and as I was dialing, I noticed debris getting kicked up under the funnel. It was only 1905Z and we were already seeing our first tornado of the day. It would not be our last.

Base velocity at 1912Z.

The storm was already severe-warned for hail, but after a couple of minutes and with our report relayed, the tornado warning was issued. We watched the tornado (not fully condensed at this point) skipping across open terrain about 2ESE Las Animas Junction or 2SSW For Lyon (Veterans Hospital). If anything, it was moving a bit to the east as it continued north toward us on the highway. I was taking pictures and video out of my window while Scott ran around and sat in the back seat behind me to do the same.

Unfortunately for us, we were fairly deep in precipitation, so we had to document from inside of the vehicle. Since I didn't have a tripod to set my video camera on, I made the biggest mistake of the day. (At some point, I'll be able to get my video up from the day, but as of now I don't have a decent way to edit the HD material in a way that I want... so it'll come in the future) As I watched a second wall cloud wrap around the first and a second tornado touch down (1t 1911Z), I wanted to get some stills, so I put my video camera in my lap and took a shot with my point-and-shoot.

Unfortunately, when I put my camera in my lap, I didn't hit "stop" and when I brought it back up to continue filming, I immediately hit the button again, which essentially stopped the recording. So, the next five awesome minutes of video will have to be relayed via this report from my memory as it is lost to history.

Please get your imagination ready:

Due to the heavy precipitation and the tornado's approach of our location on the highway, Scott evacuated the back seat and prepared to drive us out of there. Luckily, I would still be able to film since he had to drive (sigh). I watched in astounded delight as the two tornadoes began to rotate around each other, seeming to dance. Hail began to pound the vehicle as we slowly made our way to the east on US 50. Some of the hail on the highway was baseball-sized and a few large stones dented Scott's hood. I held my inactive camera out the window as we got out of the tornado's path and watched the two tornadoes twist around each other and then eventually rope and dissipate.

After the storm passed to the north of 50, we ran into Tim again and chatted with him a bit about how awesome the tornadoes were. The storm was rapidly pressing to the north at this point and we were low on fuel. So, we headed on into Lamar to fuel up. I didn't expect much to happen to the north as the storms pushed deep into the cool but moist air north of the front, so I was all about heading across the border into Kansas where storms were already starting to fire.

We were quite happy that we had scored locally and had not made the trip to Texas. Very happy indeed! As we moved east on 50 toward Kansas, we passed through a couple of cells which had previously dropped their warnings. This was a little disconcerting, but I wanted to stick to the forecast and continue east. To our northwest, our original tornadic cell was still warned and still producing tornadoes! It was hard not to second-guess our decision-making at times like this, but we really couldn't catch it anyway, so it was eastward-the-wagons.

Soon, a newly severe-warned cell was exhibiting signs of rotation as it pressed north, near Ulysses, Kansas. As we began to taste its outer fringes, the couplet strengthened significantly. There was some worry that we were not going to be in a good place but I assured Scott we'd make it through well ahead of the couplet and he trusted me and soldiered on through.

As we emerged from the precipitation, we slipped south a mile or so on a dirt road to get a better look. We were approached by a local who seemed none-too-thrilled with our presence. "Can I HELP you?" we were asked in a "why are you here" tone. We were on a main county road, so it wasn't like we were trespassing, but we decided to move along anyway and headed into Lakin.

Just south of the town, we were able to get a good look at the structure of the storm. I could see a fairly stout RFD core and then something else... it wasn't precip, but it looked like the base of the storm was on the ground. Soon, a report of a "mile-wide tornado" came across Spotter Network, so we had to go get a closer look. We drove through Lakin and headed back west on 50, keeping ourselves about a half mile from the precip core.

As my eyes adjusted, I realized that lurking in the core was a large tornado. I don't know if it was a mile wide, but it was a big fat wedge for sure.

Hartland EF-2

Base Velocity at 2156Z

The tornado quickly began shrouded in the precip as it continued to wrap around, now over the highway. We tried to get a little closer, but the RFD was howling across the road in front of us, keeping the tornado shrouded. We decided to head back to Lakin and get on the state highway 25 north to stay ahead of it. Unfortunately, we never did see it again.

We were a couple miles north of Lakin and realized that the storm was going to cross the state highway and that we would either have to progress east on dirt or go back south to get on 50 to stay ahead of it. We opted for the latter. On 50, we proceeded east to Deerfield where we found a reasonable road and headed about five miles north and then another mile back east to have a look. The area was rather low on contrast but we did our best to see what was going on.

After a few minutes, it appeared as if we were watching a distant tornado touch down. After a few seconds, we realized our eyes were not deceiving us! I have very crappy video of this tornado as I didn't have my focus set right and for whatever reason was shaking like crazy in the wind, but here's a screen shot of this tornado, which we call the "Deerfield Tornado". It was actually about 5 miles northwest of Deerfield. Near the end of my video, I remembered to check to see if I was recording, which I was. Unfortunately, Scott was not. The two of us are very paranoid now... always checking for the little red dot.

Screen shot of my video showing the distant "Deerfield" tornado. This was confirmed by other chasers in the area including Michael O'Keeffe

Velocity data at the time.

We repositioned a bit north and watched the storm try to produce again, but it couldn't quite get its act together.

We decided to avoid the temptation to travel on dirt roads at this time and retreated back down to US 50. We planned to make our next intercept on US 83 south of Scott City. Unfortunately, this would lead us away from the storm for a while. For about 45 minutes, we basically lost a good visual on the storm as we navigated through the northwest side of Garden City and then north on US 83. The storm was still warned throughout this time with an occasional tornado being reported. We finally made contact again once in Scott County. I believe we made two excursions off of the highway onto county roads to take a closer look. Both times, strong rotation was evident, but it appeared mostly that the inflow was wrapping behind the RFD core, which seemed to be becoming more prominent. Another intercept west of Shallow Water yielded the same results.

As we approached Scott City on 83, the storm was finally looking to head over the highway. A mile or two south of the city, we pulled along side the road near where TWISTEX operations were taking place. To our south, the RFD was pulsing over the road, but the rain was wrapping around rapidly... almost violently from east to west. The couplet was still very strong at this point and I was worried that there was a large tornado hiding behind the RFD curtain. As it reached us, I think we both came to the realization that it was time to go, especially when we turned around and realized no one else was still there.

We rolled into Scott City to find it deserted and under the eerie howl of the tornado sirens. The city had a lot of water on the streets but we didn't see another vehicle on the road. This was very strange as there were chasers all over the place not five minutes prior. Because we were in precipitation in the town, our visibility was not that great. I could see rapidly moving clouds overhead along with the precip, but that was about it. We turned on Kansas 96 eastbound and Scott gunned it. We were in some heavy precipitation and decent wind for a while, but then light came from behind us and it seemed that we were in a relatively dry RFD cut. Suddenly, barely to the south of the highway, I watched a rapid rotation in the clouds above. Though the rotation was rapid, it was not concentrated. Scott pulled off to the side of the road where we met a wet and frightened dog. We just sat there for a few minutes in awe as a carousel of clouds crossed the road right in front of us. The wind then shifted and rain began to wrap back around from behind us. We pulled forward a bit so that the "open carousel" circulation was directly north of us and prepared to get slammed with RFD, but that never really happened. Eventually, the circulation disappeared into the ether to the north and we found ourselves having difficulty picking out any structure. Even on radar, the storm looked to weaken.

A few miles east, we pulled off the highway between Grigston and Amy. We were fairly pleased with our results for the day... and by pleased, I mean excited! Another chaser pulled off here as well and we were thinking about leaving, so Scott flipped around but the right front tire started to sink through the soft berm of the road. We didn't want to end up in the ditch, so I hopped out and planted my feet, telling Scott to punch it (and hoping that the entire vehicle didn't roll into the ditch on top of me!). Luckily, my horizontal force pushed the vehicle right and we were stable again.

Suddenly, Scott's phone rings and it's his mom claiming that she just watched me push him out of the mud, streaming live on the internet. Sure enough, the other chaser was pointing right at us! So, we went and introduced ourselves to Mr. Randy Denzer and had a good laugh. We chatted with him for a few minutes and took a few pictures before we were on our way.

What boggles my mind is that later on, I would see a video that Randy posted showing a tornado and the sky looking precisely as it was while we were talking to him. Check out the video here (starting at 3:18 in). He said this happened after we left and since it was off to the southwest, I figure that it had to be a second cell which had formed behind, but in the same line as the first cyclic tornado-maker. I do feel stupid that we missed it. We probably only had to look behind us as we were heading east on KS 96 into Dighton.

We were thinking steak... I think that's what it was. Unfortunately, it seemed that the entire town of Dighton had shut down for the evening. We decided to head up to I-70, try our luck there and maybe get another intercept of the storms which were still heading off to the northeast. We ran into TWISTEX again near Shields and stopped to say hello, accidentally interrupting a Tim Samaras interview with our shenanigans. We chatted with Tony Laubach and Ed Grubb for a bit and while Tony saw some tornado action that day, he didn't seem too pleased.

When we left, we tried to head north on KS 23 to Grainfield, but the highway was closed for construction. At that moment, the nearby storm appeared to have a nice lowering on it, so I tried to film that for a while but it didn't come out very good as it was almost pitch black out aside from the lightning.

Our detour took us west on KS 4 and we got into a deep hail core that had almost zero visibility. It wasn't that the hail was overly large, but the quantity was extreme. The racket that it made as it pounded the vehicle was absolutely cacophonous. Scott couldn't see at all and wound up on the wrong side of the road. We just took our time out of the core, eventually making it back to US 83 and turning north with the raging thunderstorm lightning to our east keeping things interesting.

Neither of us had had a meal all day aside from a bagel many hours before so as we reached I-70, we prayed to find a place open. We were wanting steak but that soon became an unattainable goal. We ended up at the Sonic in Colby, which was seemingly the only open restaurant of any sort anywhere in northwestern Kansas. I will tell you, however, that the meal at Sonic was amazing. Was it anything special? Probably not... but after not having eaten all day, it was divine.

From there, it was on home to Denver with a full wind in our sails. Not only had we seen tornadoes that day, but both of our targets had verified. Sure, if we would have stayed in Colorado, we probably would have witnessed a few more tornadoes, but for some reason, being able to be a part of both storms ranks up there as a seriously legitimate verification. Dual-target verification!! I still get pumped up when I think about it.

I want to take a moment to reflect on a couple of things.1) I mistakenly thought that the Colorado storms would die after they crossed the boundary, but in reality, the low level winds were even more conducive for tornadoes and while the temperatures were cooler, the air was very moist. There were a lot of tornadoes north of the boundary!

2) What an incredible storm the Lakin-Scott City supercell was! Throughout its life cycle, it maintained a very strong couplet with multiple mesocyclonic circulations wrapping in and continuously producing tornadoes. We missed several of these but did see two, including the EF-2 Hartland wedge. A second supercell that formed on its heels eventually caught up with the first and they seemed to merge eventually north of Dighton. Awesome storm!

3) Our positioning on the Kansas storm could have been better. After pouring over others video of some of the tornadoes that we missed and even our own experiences with the storm, it appeared that a better observation point may have actually been the back side of the storm where many of the tornadoes were accompanied by a decent and continuous clear slot. Most of the time, we seemed hampered by wet RFD wrapping back into the main circulation.

I definitely feel that while this was a successful chase, I learned a lot of important lessons, including but not limited to: MAKE SURE YOU ARE RECORDING!

Wednesday, November 10, 2010

What fantastic weather we have had here in Denver for the past week! Temperatures cruised up into the 70s on a few occasions and it felt as if winter was never going to come. Those of us who spend most of our time watching the weather, however, knew that this warmth was short-lived.

Models had been consistent in bringing a deep trough into the west, which would break down the pleasant ridge we had been living under seemingly since summer. There didn't seem to be much question as to whether the precipitation would fall as snow or not. It definitely would be cold enough. So, today I watched as the cold front pushed through early this morning and set us up into deep upslope for the day. The radar began to pick up returns along the Front Range while it was still sunny across the Urban Corridor.

I started looking a little more closely at the RUC and saw a bit of instability as well, which made sense since lapse rates were decent. Sure enough, lightning began to show up in the mountains. Over the next couple of hours, the clear skies over the metro gave way to a rapidly moistening atmosphere. The radar returns began to reach over the Footies and then into the Urban Corridor. I decided to head outside with my camera to have a look.

A bit of a shelf cloud forming on the outflow from snow showers moving out of the mountains.

As the precipitation grew eastward, cold air began to descend out of the mountains, undercutting the upslope. While I was standing there taking photos, I endured a few spits of light rain but this was soon replaced with sleet. The sleet surprised me. I had predicted graupel with the available instability, but not the sleet. I had to think for a bit to figure out how it happened and as far as I could tell, it was just the undercutting of the upslope flow by the cold pool. That allowed the rain to fall through the subfreezing air close to the ground and become an ice pellet. Soon, the pellets falling changed from clear, frozen rain drops to white, accreted snow pellets or graupel. I kind of love graupel. In fact, way back when in high school, I wrote an article for the local newspaper in Butte, Montana about the difference between graupel and hail since I was tired of people telling me that they had been hailed on during a convective snow shower. If you're curious about the processes, I'll explain it briefly here. Graupel is formed in the same manner as a hailstone with the main difference being that for graupel, the entire depth of the convective cloud is below freezing. The snow pellet is formed by accretion of ice crystals as it travels up and down in the storm's updraft. For hail, the freezing layer is usually higher up in the cloud and thus the "stone" when traveling up and down in the updraft spends some time accumulating water and then having it freeze when it is higher.

Anyway, I figured we would see some graupel and we most certainly did! I was hoping for some larger pellets, but most were fairly small.

Back at my apartment, the graupel actually changed back into rain for a while before snow slowly started mixing in. Over the next hour or so, it actually started snowing large dendrites for maybe a half hour. Most of these melted, but eventually the snow began to accumulate on grassy surfaces. I figured it was high time to fire up the fireplace and make some hot cocoa! All weather should be enjoyed...

I was content to spend the rest of the evening indoors, but I caught a glimpse of color outside of my window and noticed that the sunset might be peeking through. I put on my warm clothes and got my camera again, making my way back out to the empty lot east of my apartment complex. Unfortunately, the small hole in the stratus that let the sunset through had closed up, but I figured since I was out, I might as well make the best of it. So, for the next hour, I walked around the Greenwood Plaza area and took pictures, occasionally being startled by a flash of light or two in the sky. Interestingly, the precipitation was almost over, but I kept seeing flashes.

Russian Olive after the snow.

Snow on the top of Plaza Tower One.

City lights of Denver reflecting off of the stratus deck with the Landmark towers almost hitting their heads on the ceiling.

Evening traffic at South Syracuse Way and East Caley.

"The Cascades"

Another trip through the Museum of Outdoor Art.

The Weidenblume

Village Center

It was actually a beautiful evening to go out for a bit of a walk. It wasn't too cold and just nice to be "experiencing" the first snow of the year. Even at home later in the evening, I would occasionally see a flash in the sky outside. I still find this strange as most of the precipitation had moved well off to the east, but I am unable to explain it otherwise.

About This Blog:

"Always Chasing" describes my desire to never stop pursuing my goals and dreams (pardon the cliché). There are always storms to chase and trails to explore. This blog is a repository of those adventures... pursuing severe/adverse weather, visiting new places and exploring the natural topography of my surroundings. It is an outlet for my amateur pursuit of photography with my point-and-shoot camera as well as a forum for discussing meteorological events. The name "Big Sky Convection" will remain, but I feel that "Always Chasing" more accurately describes my direction.